This application claims the priority of German patent document 199 44 540.0, filed 17 Sep. 1999, the disclosure of which is expressly incorporated by reference herein.
The invention relates to a reactor system, for reacting a hydrocarbon or hydrocarbon derivative charging material, having a catalyst-coated reaction chamber, to which a reaction educt stream can be fed through a reaction chamber inlet, and electric heating means.
European patent document EP 0 757 968 A1 describes a reforming reactor for catalytic combustion of methanol and oxygen or oxygen-containing gas in a reaction chamber. For the catalytic combustion, the reaction educts are fed to an internal region of the reaction chamber through a supply channel, projecting into the interior of the catalyst-filled reaction chamber. In the region of the opening of the supply channel in the interior of the reaction chamber there is an electric heating coil, with which in the warmup operating phase catalyst material, located at the opening, can be raised rapidly to a temperature suitable for the catalytic reaction. Reaction educts, which flow through the opening of the supply channel into the reaction chamber, are heated by the exothermic reaction in the vicinity of the heating coil, thus heating the other areas of the reaction chamber. After a startup operating phase, when a desired operating temperature has been reached in the whole reaction chamber, the heating coil can be switched off.
German patent document DE 33 45 958 A1 describes a hydrogen-producing reforming reactor for reforming methanol. Said reforming reactor comprises a burner, where fed-in methanol is burned with air in a start operating phase, thus quickly heating the reforming reactor to an optimal operating temperature.
U.S. Pat. No. 3,982,910 discloses a hydrogen-producing, catalytic reactor for reacting a hydrocarbon with an admixture of air. In a warmup operating phase liquid hydrocarbon and air are fed through a fuel nozzle into the reactor and ignited by a spark plug. Owing to the exothermic combustion reaction, the reforming reactor quickly reaches its operating temperature. It then serves to partially oxidize the evaporated hydrocarbon.
Japanese patent document JP 3-218902 (A) discloses a hydrogen-producing, catalytic reforming reactor for reforming vaporous methanol. The reforming reactor comprises a catalytic burner, where a mixture of methanol vapor and air is burned during a warmup operating phase in order to quickly reach an optimal working temperature for the gas mixture that is to be reformed and is fed into the reforming reactor.
Japanese patent document JP 7-315802 (A) describes a hydrogen-producing, catalytic reforming reactor, with an electric heater comprising resistor elements embedded into the catalyst material in the reforming reactor, and energized with a battery. By operating the heater in a start operating phase, the reforming reactor and its entire reactor volume are supposed to be raised to a temperature that is optimal for the reforming reaction. Similarly, Japanese patent document JP 58-219945 (A) discloses a cylindrical reforming catalyst body with grate-shaped cross sectional structure, whose openings are laced with electric heating wires in order to raise the reaction chamber-forming catalyst body rapidly to the operating temperature.
Published European patent document EP 0 913 357 A1 discloses a class of reactor system which includes a catalyst-coated electric heater, that is permeable to the reaction educt stream and has, for example, a porous or honeycombed structure. It is spaced at a distance from the reaction chamber inlet of a catalyst-coated reaction chamber, which is formed by a catalyst body housed with the heater in a joint housing. As an alternative, the heater can be dispensed with and the catalyst body itself can be designed so as to be electrically heatable. Similar reactor systems with a reaction chamber-forming catalyst body and an electric heater, which is located upstream at a distance, are described in the subsequently published European patent document EP 0 967 174 A1 and British patent document GB 2 268 694 A.
The object of the present invention is to provide a reactor system of the type described above, which has good cold start properties.
This and other objects and advantages are achieved by the reactor system according to the invention, in which the reaction chamber inlet has a flat, electrically heatable, catalyst-coated, and reaction educt stream-permeable heater, which covers at least partially the inlet cross section of the reaction chamber inlet. The educts for reacting the charging material can be fed through the permeable heater, at least in a start operating phase of the reactor system.
In one embodiment of the invention, there is an electric heater in front of the reaction chamber inlet, for heating at least one reaction educt in a start operating phase, and there are means for point-by-point injection of at least one reaction educt, heated in the heater, into the reaction chamber. Thus, the invention facilitates in a start operating phase an especially efficient, fast heating of the reactor system to the operating temperature.
In another embodiment of the invention, the heater has several heating elements, which collectively cover the inlet cross section of the reaction chamber, either totally or partially. In this manner a very small amount of electric energy, distributed over the inlet cross section at several points, will trigger a catalytic combustion reaction. At the same time the resulting heat will spread quickly through the entire reaction chamber owing to thermal conductance.
In still another embodiment of the invention, the heater has a heating disk, which completely covers the inlet cross section of the reaction chamber. In this manner a reactor system is created that can be raised comparatively quickly to the operating temperature in the case of a cold start.
Finally, in yet another embodiment of the invention, the reactor system comprises a switchable reaction educt feed system with feed means, which feed the reaction educt stream to the reaction chamber in a start operating mode, only over one part of the inlet cross section of the same; and in a normal operating mode over the entire inlet cross section. In this manner the feed of reaction educts can be adjusted to the varying requirement in the start operating mode, on the one hand, and in the normal operating mode, on the other hand.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.